Intrinsic tensile properties of cocoon silk fibres can be estimated by removing flaws through repeated tensile tests (original) (raw)
Related papers
Scientific Reports, 2022
Silk fibres attract great interest in materials science for their biological and mechanical properties. Hitherto, the mechanical properties of the silk fibres have been explored mainly by tensile tests, which provide information on their strength, Young’s modulus, strain at break and toughness modulus. Several hypotheses have been based on these data, but the intrinsic and often overlooked variability of natural and artificial silk fibres makes it challenging to identify trends and correlations. In this work, we determined the mechanical properties of Bombyx mori cocoon and degummed silk, native spider silk, and artificial spider silk, and compared them with classical commercial carbon fibres using large sample sizes (from 10 to 100 fibres, in total 200 specimens per fibre type). The results confirm a substantial variability of the mechanical properties of silk fibres compared to commercial carbon fibres, as the relative standard deviation for strength and strain at break is 10–50%....
Journal of Polymer …
Regenerated silkworm fibers spun through a wet-spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk.
Study on the Mechanical Properties of Different Silkworm Silk Fibers
Journal of Composite Materials, 2009
Mechanical properties of Bombyx mori, twisted B. mori, and Tussah silk fibers were investigated. Their ultimate tensile strength, elongation at break, and Young’s modulus were examined by performing a uniaxial tensile test on a single fiber. Scanning electron microscopy was used to observe the morphology of two different types of silk fiber, and to measure their apparent diameters from which the cross-sectional area of the silk fiber for stress-strain analysis can be determined. Based on experimental results obtained, it was found that Tussah silk fiber has a relatively high extensibility as compared to B. mori silk fiber and other natural fibers. Weibull analysis was also used to quantify tensile strength reproducibility of the silk fiber. Both single and twisted B. mori silk fibers have a better reproducibility of tensile properties than Tussah silk fiber.
Mechanical properties and toughening mechanisms of natural silkworm silks and their composites
Journal of the Mechanical Behavior of Biomedical Materials, 2020
There is an emerging interest in natural silkworm silks as alternative reinforcement for engineering composites. Here, we summarize the research on two common silkworm silks and silk fibre reinforced plastics (SFRPs) from the authors over the past few years in the context of related research. Silk fibres from silkworms display good strength and toughness under ambient and cryogenic conditions owing to their elastic-plastic deformation mechanism. In particular, the wild Antheraea pernyi (A. pernyi) silk also displays micro-and nano-fibrillation as an important mechanism for toughness and impact resistance. For SFRP composites, we found: (i) it is critical to achieve silk fibre volume fraction to above 50% for an optimal reinforcement and toughening effect; (ii) the tougher A. pernyi silks present a better reinforcement and toughening agent than B. mori silks; (iii) impact and toughness properties are advantageous properties of SFRPs; (iv) hybridization of natural silk with other fibres can further improve the mechanical performance and economics of SFRPs for engineering applications; and (v) the lightweight structure designs can improve the service efficiency of SFRPs for energy absorption. The understanding on the comprehensive mechanical properties and the toughening mechanisms of silks and silk fibre-reinforced polymer composites (SFRPs) could provide key insights into material design and applications.
Variability in mechanical properties of Bombyx mori silk
Materials Science and Engineering: C, 2007
In the present paper, the variability of mechanical properties of Bombyx mori silk is investigated at the intraspecific and intraindividual levels. We first reeled some complete silks of 700-1500 m in length from cocoons in a special procedure. A large number of tensile tests were performed to measure the variations of Young's modulus, ultimate tensile strength, yield stress, elongation and breaking energy of an entire silk along its length direction. Our experimental results and statistical analysis show that the diameter and mechanical properties of silk have significant variabilities at both the intraspecific and intraindividual levels. On one hand, this indicates that a single silkworm silk seems inappropriate to be applied as an engineering material to bear loading. On the other hand, however, it is interesting to note that the variability of silk does not exist as a disadvantage for a cocoon to achieve a superior ability against possible attacks from the outside. In addition, the dependence of such parameters as Young's modulus and tensile strength upon the diameter of silk was also analyzed, and distinct size effects were observed in these properties. This study not only provides a deeper understanding of the mechanical properties of silks and cocoons but is of interest for the design and tailoring of advanced biomimetic silk materials also.
Tensile mechanical property evaluation of natural and epoxide-treated silk fibers
Journal of Applied Polymer Science, 1995
Silkworm cocoon silk and spider major ampullate (drag line) silk exhibit macroscopic tensile properties that, while impressive in the context of polymer fibers, are highly variable. T h e variability is linked t o the cross-sectional geometry being nonuniform: silk fiber cross section changes significantly over distances t h a t are small compared t o t h e scale on which diameters are averaged by typical characterization techniques. This characteristic must be taken into account when evaluating chemical treatments (in the present case infiltrating with crosslinkable epoxide) that are aimed a t improving strength or stiffness. The magnitude of any change in mechanical property must be considered in relation to the spread in values recorded prior to treatment. An apparent improvement in the mean value of a tensile property may turn out to be statistically insignificant when compared to the standard deviations associated with those data.
Comparison of Physical Properties of Three Silks
Orb-web weaving spiders synthesize and use a variety of silks, each having different propertie s suited to their particular functions . Three of these silks were collected from two different species of spiders an d subjected to physical/mechanical testing . The major ampullate (dragline), minor ampullate, and cocoon silks o f both Nephila clavipes and Araneus gemmoides were load tested on an Instron Universal test frame to compar e their physical properties . The single fibers of major, minor, and cocoon silk of Nephila appear to be more elastic than that of Araneus . Araneus silks, on the other hand, appear to be stronger, requiring a higher stress to brea k the fiber than that of Nephila .
Ultrastructure of Insect and Spider Cocoon Silks
Biomacromolecules, 2006
Despite much interest in the extraordinary mechanical properties of silks, the structure of native silk fibers is still not fully understood. In the present study, the morphology, topography, and organization of insect and spider cocoon silks were investigated using a range of imaging methods. Field emission scanning electron microscopy was used to observe transverse and longitude structures in silk fibers subjected to tensile fracturing, freeze fracturing, or polishing. In addition, ultrathin sections of silk brins embedded in resin were examined using transmission electron microscopy. Finally, dry silk brins were examined by confocal microscopy. The results confirmed the existence of well-oriented bundles of nanofibrils in all the silks examined and gave an indication of a hierarchical construction of the brin. Observed separation of the microfibrils in fractured brins suggests that the multifibrillar structure of the silk fiber contributes to toughness by allowing dissipation of energy in the controlled propagation of cracks.
Engineering Properties of Spider Silk Fibers
Natural Fibers, Plastics and Composites, 2004
Motivated by the high level of strength and toughness of spider silk and its multifunctional nature, this paper reports on the engineering properties of individual fibers from Nephila Clavipes spider drag line under uniaxial tension, transverse compression and torsional deformation. The tensile properties were compared to the Argiope Aurentia spider silk and show different ultimate strength but similar traits of the unusual combination of strength and toughness characterized by a sigmoidal stress-strain curve. A high level of torsional stability is demonstrated. comparing favorably to other aramid fibers (including Kevlar fibers).
Journal of Raman Spectroscopy, 2014
The comparison of the low wavenumber of polarized Raman spectra (50-300 cm -1 ) from Bombyx mori (fresh cocoons fibres, handstretched 'Crins de Florence' strings from the gland content, dried gland, regenerated silk films) and Nephila madagascarensis silks reveals the high polarisation of fibre modes and the absence of polarisation for dried gland and regenerated silk films. This is consistent with X-ray diffraction measurements. The orientation of the fibroin/spidroin chains is due to the stretching during production, as for advanced synthetic fibres. The bandwidth of the 'ordered chains' signature is almost the same for the different fibres. However, the degree of polarisation seems to be higher in the case of spider fibre. The huge bandwidth of low wavenumber components of regenerated films indicates high disorder. Measurements along the fibre point out conformation changes with a periodicity (~20 mm) related to the silkworm head motion during the fabrication of the cocoon.